1. Field of the Invention
The present invention relates to a gasket.
More particularly, the present invention relates to a gasket for a case, which is made of a low rigidity material such as synthetic resins, aluminum or the like, and is used for electronic apparatuses or the like.
2. Description of the Conventional Art
In a case cover for electronic apparatuses or the like, which is made of a low rigidity material such as synthetic resins or the like, a gasket having a low reaction force and having a low change rate of the reaction force to the compression amount has been conventionally, mainly used. The gasket has been adopted from the viewpoint of preventing deformation of a cover and securing sealing ability to the variation of dimensional accuracy (following the partial variation of the compression amount) at the time of fastening.
As a kind of the gasket, the following gasket illustrated in FIG. 5 has been known (Japanese Utility Model Laid-Open No. 62-108661). The gasket includes a body section 310 which is inserted in a mounting groove not illustrated, two lines of support protrusions 320 and 330, which are provided on the bottom side of the mounting groove of the body section 310 and extend in parallel with the body section 310, and a lip ridge protrusion 340 which is provided on the other side of the body section 310.
Further, the gasket includes an aperture 350 formed so as to have a shape capable of absorbing the compression of a rubber-like elastic material, on the bottom side of a mounting groove on the surface opposed to the lip ridge protrusion 340.
However, even having the aforementioned shape, the gasket 300 is not a satisfactory gasket for low reaction force with respect to a case, which is made of a low rigidity material such as synthetic resins, aluminum or the like and is used for electronic apparatuses or the like.
Then, a gasket 300 having a shape illustrated in FIG. 6 has been proposed (Japanese Patent Application Laid-Open No. 2004-39341).
Namely, the gasket 300 is constituted with a body section 310 inserted in a mounting groove 100 of a case (one member) 100, and a lip ridge protrusion 340 provided on another side of the body section 310. The lip ridge protrusion 340 has a shape extending in a tilted manner toward the body section 310.
Therefore, as illustrated in FIG. 7, it can be expected to realize low reaction force of the lip ridge protrusion 340 and improve its followability at the time of gripping the lip ridge protrusion 340 between one member 100 and the other member 200 so as to be in pressure contact with the two members.
However, as for such the lip ridge protrusion 340 having a structure in a tilted manner, when the gasket 300 is formed and released, the lip ridge protrusion 340 is removed forcibly. Therefore, if the lip ridge protrusion 340 has a steeply tilted shape, there are problems that the lip ridge protrusion 340 is damaged easily so that the operability is low, or the like.
On the other hand, if the tilted angle of the lip ridge protrusion 340 is small, low reaction force is hardly made even if the lip ridge protrusion 340 falls, and the change of reaction force to the compression amount increases. In addition, the lip ridge protrusion 340 to hardly falls in the fixed direction as planned, and there is a possibility that the lip ridge protrusion 340 may partially fall in the opposite direction. As a result, lowering the sealing ability is caused.